The pseudonymous Farrell's formidably long and richly detailed fantasy debut launches a new series that's sure to delight fans of Celtic fiction. A magic talisman that holds the fate of the world falls out of the sky onto the tale's naïve, 17-year-old heroine, Jenna Aoire, one night while she's herding sheep on Knobtop Hill with her dog outside the village of Ballintubber. The pebble-sized object, which turns out to be the Cloudmages' master spell-stone, the Lámh Shábhála, soon leads to trouble for Jenna and her mother, who must flee for their lives from their enraged neighbors. They come under the protection of the House of Mac Ard, but treacherous lords who covet the spell-stone ensure no rest for the weary refugees. In this thinly disguised medieval Ireland, every man's hand can be turned against every other's (and women aren't backward in the fight, either), particularly when the stakes are as high as they are here. Much intrigue involving a multitude of mostly well-drawn characters and little bloodshed make for a relatively leisurely plot by the standards of this subgenre. Powerful scenes of magic-wielding and the vividly depicted Celtic society, though, should hook persistent readers, who will be glad for the glossary of character and place names, a guide to the Daoine calender, a list of the holders of the Lámh Shábhála and more at the end of this challenging book. (Jan. 7)